Paddle arrangements for powderless etching machines

ABSTRACT

An improved paddle arrangement for powderless etching machines for directing the etchant against the surface of a photoengraving plate. A plurality of paddle assemblies are located between the etching bath and the plate and are rotatable about parallel horizontal axes of a selectively variable speed. Each assembly includes a plurality of paddles having variously angled outer end portions. The relation of the paddle edge angles of each assembly in cooperation with those of the adjacent assemblies provides a uniform distribution and the equivalent effect of a substantially perpendicular direction of the etchant against the plate surface during rotation of the paddle assemblies at any speed within the normal operating range, thereby eliminating the need for the conventional baffles between the paddle assemblies.

United States Patent [72] Inventors Louis E. Zeller Warminster; RobertJ. Patsko, Merlon, both of Pa. 21 Appl. No. 859,389 [22] Filed Sept. 19,1969 [45] Patented Dec. 14, 1971 [73] Assignee Master Etching MachineCo., Inc.

Ambler, Pa.

[54] PADDLE ARRANGEMENTS FOR POWDERLESS ETCHlNG MACHINES 7 Claims, 7Drawing Figs.

[52] U.S. Cl 156/345, 134/194 [51] Int. Cl C23g 3/00 [50] Field ofSearch 156/345, 14; 134/193, 194,183, 107

[56] References Cited UNITED STATES PATENTS 2,669,048 2/1954 Easley etal 134/107 2,776,512 l/l957 Guenst ABSTRACT: An improved paddlearrangement for powderless etching machines for directing the etchantagainst the surface of a photoengraving plate. A plurality of paddleassemblies are located between the etching bath and the plate and arerotatable about parallel horizontal axes of a selectively variablespeed. Each assembly includes a plurality of paddles having variouslyangled outer end portions. The relation of the paddle edge angles ofeach assembly in cooperation with those of the adjacent assembliesprovides a uniform distribution and the equivalent efi'ect ofasubstantially perpendicular direction of the etchant against the platesurface during rotation of the paddle assemblies at any speed within thenormal operating range, thereby eliminating the need for theconventional baffles between the paddle assemblies.

PATENTEU DEC 1 4 I971 SHEET 1 BF 3 mvcu'ronsz. LOUIS E. ZELLER ROBERT JPATSKO AT TYS.

PATENTEDDEBMISYI 3.627.614

SHEET 3 OF 3 FIGS INVENTORS'.

LOUIS E. ZELLER ROBERT J. PATSKO zmwf/ w ATTYS PADDLE ARRANGEMENTS FORPOWDERLESS ETCI-IING MACHINES The present invention relates generally toetching machines for etching photoengraving plates and relates morespecifically to improvements in etching machines of the type employedfor carrying out the Dow powderless process.

Etching machines of the general type to which the present invention isdirected are shown for example in U.S. Pat. Nos. 2,669,048, 2,700,838and 2,776,512. This type of machine is characterized by a tank adaptedto contain a liquid etching bath which is maintained at a predeterminedlevel, a cover for the tank beneath which the plate to be etched issupported face down in spaced parallel relation with the surface of theetching bath, means providing some type of planar motion of the plate,and means for directing etchant from the bath against the plate. Asshown in the above-mentioned patents, the conventional means fordirecting etchant against the plate comprises a plurality of rotatablepaddles provided with spaced vertical baffles therebetween, the paddlesextending into the etching bath and in conjunction with the bafflesdirecting a generally vertical stream of etchant against the plate faceto effect the desired etching thereof.

It is well understood in the art that in order to prevent undercuttingand bleeding of the photoengraving, the etchant must not be permitted toflow across the plate surface. Since the paddles are rotated at arelatively high speed, normally within a range of 300-1,000 r.p.m., theplate is accordingly subjected to a rapid succession of ribbons ofetchant from the paddles. The paddle edge portions are conventionallyangled at about 30 to provide an approximately vertical release of theetchant. However, since the speed of rotation of the paddles isvariable, a single paddle angle cannot be relied on to give a verticaldirection of etchant. At a higher speed the etchant is released earlier,and at a slower speed remains on the paddle for a later release. Forthis reason the conventional baffles are employed between the paddleassemblies and are carefully adjusted to direct the etchantsubstantially vertically against the plate.

The present invention eliminates the need for baffles by providingpaddle assemblies in which the paddle edge portions are variously angledin a predetermined relation. In a preferred embodiment, each assemblyincludes a pair of diametrically opposed blades, one having an edgeportion angled at 30, the other having an edge portion angled at 60. Inoperation, the angular release of etchant from the perpendicular by the30 paddle is offset by the release from the 60 paddle of the adjacentassembly. Although the release angles will vary somewhat with speedchange, the offsetting effect of the adjacent angled paddles willprevent the development of etchant flow across the plate surface andprovide the equivalent effect of a substantially perpendicular directionof the etchant against the plate surface.

With the present invention, the expense of installing and adjusting thebaffles is completely eliminated. Furthermore, the absence of thebaffles permits a more thorough mixing of the etching bath and hence ahigher quality etching of the plate. In a process which is alreadycomplicated by a large number of critical variables, the elimination ofthe bafi'les simplifies the process by removing a mechanical elementwhich required careful adjustment. The baffles in addition due to theirenvironmental location between the paddle assemblies attractcontaminants in the form of concentrated etchant additives which canhave a deleterious effect on the etching process.

It is accordingly a first object of the present invention to provide animproved paddle arrangement for powderless etching machines whichprovides a unifomi distribution of etchant against a photoengravingplate surface over the normal operating speed range of the machine.

A further object of the invention is to provide the improvement asdescribed which effectively eliminates the need for bafiles between thepaddle assemblies.

Another object of the invention is to provide the improvement asdescribed which may be easily and economically fabricated and which mayreadily be adapted to convert conventional etching equipment.

Additional objects and advantages of the invention will be more readilyapparent from the following detailed description of embodiments thereofwhen taken together with the accompanying drawings in which:

FIG. 1 is a front elevational view of an etching machine incorporatingthe present invention with a portion thereof broken away to show theinterior arrangement of the machine;

FIG. 2 is an enlarged view of the rectangular area of FIG. 1 enclosed inbroken lines schematically showing the etchant directing action of thepaddle assemblies at a particular speed of rotation;

FIG. 2a is a view similar to FIG. 2 schematically showing the action ofthe paddles at a higher speed of rotation;

FIG. 3 is an enlarged end view partly in section of one of the paddleassemblies showing the configuration of the paddles carried thereon;

FIG. 4 is a side view of the paddle assembly shown in FIG. 3;

FIG. 5 is an end view partly in section showing a modified form ofpaddle assembly; and

FIG. 6 is an end view partly in section showing a further modified formof paddle assembly.

Referring to the drawings and particularly FIG. 1 thereof, an etchingmachine generally designated 10 is illustrated of a type adapted forcarrying out a powderless etching process and includes a frame 12supporting a tank 14 adapted to contain an etching bath 16 which ismaintained at a level 18. A tank cover 20 is pivotally mounted on coversupports 22 in a conventional manner permitting the cover to be openedfully when the machine is not in operation.

A plate support member 24 having clamps 26 adjustably attached theretofor securing a photoengraving plate 28 therebeneath is rotatablysupported beneath the cover on shaft 30 which extends through the coverinto the plate drive mechanism within the housing 32. This mechanism isof a conventional type and may impart either a rotational or a planetarymotion to the plate 28 in the plane of the plate during operation of themachine.

A plurality of paddle assemblies 34 are located within the tank 14between the etching bath and the plate 28. The assemblies 34 includepaddle shafts 36 which are arranged in uniformly spaced parallelhorizontal relation. Mounted on each paddle shaft 36 are a pair ofpaddles 38, the outer end portions of which upon rotation of the paddleshafts pass through the etching bath and serve to direct the etchantonto the downwardly facing surface of the photoengraving plate. Thepaddle shafts 36 which are joumaled at each end by bearings (not shown)on the outer walls of the tank, are driven in rotation by the motordrive unit 40 mounted on the frame 12 below the tank by means of aplurality of drive belts 42 which pass around a drive sheave 44, idlersheaves 46 and similar sheaves on the ends of the paddle shafts. Bymeans of this conventional drive arrangement, the paddle shafts are alldriven in the same direction at the same speed. Suitable motor controlmeans (not shown) are provided to permit a selective variation of thespeed of rotation of the paddle assemblies, and a normal range ofoperation might for example be 300-] ,000 rpm.

The machine 10 as described thus far is of a conventional constructionand the described elements and their functions are similar to thecorresponding elements of the patents referred to above. The operationof the present machine is generally similar to those of the prior art inthe sense that the etchant is driven by the paddle assemblies againstthe surface of the photoengraving plate mounted in spaced relation abovethe etching bath, the plate being moved in a circular or other motion inits plane to insure uniformity of the etching action.

The novelty of the present invention is in the paddle assemblies andspecifically in the angular relationship of the paddle edge portions ofeach assembly. The angling of the outer edge of a paddle will determinethe angular direction in which the etchant picked up by the paddle isreleased at a given speed of rotation of the paddle. For a given speedof operation, it is possible to select a paddle angle which will producea substantially vertical direction of release of the etchant. Theetchant will, of course, tend to spread out upon release into afanshaped spray which will impact on the photoengraving plate in a zoneof substantial width. Accordingly it is the average direction which isreferred to in the present discussion.

Although a substantially vertical release direction could be obtainedfor a given speed, only an area of narrow width directly above thepaddle at the time of release would receive the desirable trulyperpendicular etchant delivery. Since the etching action is dependent onthe impacting of the etchant against the plate, a deeper etch willresult directly above the paddle even if it were possible to obtain anaverage vertical release direction.

Etching machines of this type, however, must be operable over arelatively wide speed range. Accordingly, if a given paddle angle werefound suitable for one speed to direct the etchant in a substantiallyvertical direction, at a faster or slower speed the release would be atan earlier or later time and the angle of release would be changedaccordingly. Conventional machines are thus provided with verticalbaffle plates between the paddle assemblies, and a uniform paddle edgeangle, for example 30, is utilized to lift the etchant toward the plate.The use of baffles does not, however, eliminate the problem of unevenetching action since the most effective etching action occurs directlyabove the baffles.

in the present invention, it is possible to eliminate the conventionalbaffles due to the employment of a specific angular relationship of thepaddle edges of each paddle assembly which in cooperation with the samerelationships of the paddle edges of the adjoining assemblies produces aresultant delivery of etchant against the photoengraving plate havingthe equivalent effect of a substantially perpendicular direction ofetchant against the plate surface over the normal operating speed rangeof the machine. Referring to FIGS. 3 and 4, the preferred paddleassembly construction includes a pair of paddles 50 and 52 formed ofsheet metal and mounted on the paddle shaft 36 in substantiallydiametrically opposed relation by the bolts 54 extending therethrough.The manner of attachment of the paddles to the shaft is not ofimportance and the blades may alternately be welded or otherwise securedto the shaft.

The paddles each include a substantially radially extending portion 50aand 52a and an angled outer end edge portion 50b and 52b. Asillustrated, the edge portion 50b is angled at 30 to the radiallyextending portion 500, while the edge portion 52b is angled at 60 to theradially extending portion 52a.

In operation, the present paddle arrangement functions in the mannerschematically indicated in FIGS. 2 and 2a. In FIG. 2, the paddleassemblies are depicted as rotating at a moderate speed and thecooperation function of the variously angled paddles is indicated by thebroken line zones of etchant delivery A and B respectively for paddles50 and 52. It will be noted that zones A and B overlap substantially inthe regions C in which the etchant is delivered at opposing angles fromthe adjoining paddle assemblies. Any tendency for etchant flow todevelop along the plate is stopped by the counteracting flow forces inthe regions C. in addition the counteracting flow in the regions Cenhances the etching action which otherwise would be least effective inthese regions due to their distance from the delivery points of thepaddles.

At a higher speed illustrated schematically in FIG. 2a, the zonesproduced by the paddles 50 and 52 are shifted somewhat to the left asshown at A and B but the regions C of overlap are present and providethe same flow curbing function. it may thus be understood that thetendency of a 30 paddle of one assembly to induce a flow of etchantalong a plate is counteracted by the tendency of a 60 paddle of theadjoining assembly to induce a flow in the opposite direction.

Experiments utilizing a glass topped machine were carried out utilizingall 30 paddles without baffles and a visibly apparent flow of etchant inone direction across the plate could be observed. Using all 60 paddles,a similar flow in the opposite direction resulted. With the presentcombination of 30 and 60 paddles, no perceptible flow could be detected.The

quality of photoengravings processed with the present paddle arrangementhas been excellent.

Although the paddle assemblies should all rotate in the same direction,the direction itself is unimportant. Similarly, due to the high paddlespeed, it is not necessary that the paddle assemblies operate with theuniform paddle alignment shown in the drawings. Belt slippage will infact produce a random orientation of the assemblies.

In FIG. 5 a modified form of the preferred paddle assembly embodiment isillustrated. in this form, the paddles 60 and 62 differ from thepreviously described paddles 50 and 52 only in that the edge portions60b and 62b are curved from the radially extending portions 60a and 62a.The effective angles of 30 and 60 are maintained and this form functionsin exactly the same manner as that previously described. It should benoted that the length of the angled edge portions is determinative onlyof the volume of etchant delivered, the edge angle being the determiningfactor as to when the etchant is released.

in FIG. 6 a further modified form of paddle assembly is illustrated.This form comprises six paddles, 70-75, each of which includes radialportions, 70a-7Sa, secured to a collar on shaft 82 such as by welding.The outer edge portions 70b-75b of the paddles are formed at variousangles as indicated to produce the uniform etching action describedabove.

Specifically edge portions 70b, 71b and 72b are respectively formed at23, 30 and 37 to their paddles radial portion. These paddles effectivelycarry out the function of the 30 paddle of the preferred embodiment.Similarly, edge portions 73b, 74b and 75b are angled respectively at 53,60, and 67 to their paddles radial portions, thus effectively carryingout the function of the 60 paddle of the preferred embodiment.

In operation, paddle assemblies such as shown in FIG. 6 operate in thesame manner as described above, with the etchant delivered by the 23, 30and 37 paddles being counteracted by that delivered by the 53, 60 and 67paddles of adjoining assemblies.

A number of other combinations of paddles having variously angled edgeportions may be employed within the scope of the invention. For example,four equally spaced paddles having 30, 60, 30, and 60 edge portions.Another example is an assembly of four paddles of 25, 35, 55 and 65.These examples are not meant to be exhaustive and the desired uniformetching effect can be obtained with variously angled blades in theranges substantially of 23"-3 7 and 5367 provided a suitablecounterbalance is maintained.

Manifestly, changes in details of construction can be effected by thoseskilled in the art without departing from the spirit and the scope ofthe invention as defined in and limited solely by the appended claims.

We claim:

1. in an etching machine having a tank adapted to contain an etchingbath, means for supporting a photoengraving plate above the etchingbath, a plurality of paddle assemblies rotatably disposed between theplate and the etching bath adapted to direct etchant from the etchingbath against the photoengraving plate, and selectively variable meansfor rotating said paddle assemblies within a range of operating speeds,the improvement wherein each said paddle assembly comprises at least twopaddles having outer edge portions adapted to pass through the etchingbath, the paddle outer edge portions being angled with respect to theradial portion thereof in the direction of paddle rotation, and means onsaid paddles 2. The improvement as claimed in claim 1 wherein each saidpaddle assembly includes a first paddle having an outer edge portiondisposed at an angle substantially within the range 2337, and a secondpaddle having an outer edge portion disposed at an angle substantiallywithin the range 53-67.

3. The improvement as claimed in claim 1 wherein said paddle assemblyincludes a first paddle having an outer edge portion disposed at a 30angle, and a second paddle having an outer edge portion disposed at a 60angle.

4. The improvement as claimed in claim 3 wherein said first and secondpaddles are in diametrically opposed relation on the paddle assembly.

5. In an etching machine having a tank adapted to contain an etchingbath, means for maintaining the bath at a predetermined level, means forsupporting a photoengraving plate above the etching bath in spacedparallel relation with the surface of the bath, means for providingplanar movement of said photoengraving plate, a plurality of paddleassemblies having spaced parallel horizontal axes rotatably disposedbetween the plate and the etching bath and adapted to direct etchantfrom the etching bath against the photoengraving plate, and selectivelyvariable means for rotating said paddle assemblies within a range ofoperating speeds, the improvement wherein each said paddle assemblycomprises a plurality of paddles, each paddle including an innerradially extending portion and outer edge portion, the outer edgeportions of the paddles of each assembly being variously angled withrespect to the radially extending portions in the direction of rotationof the as sembly, a first paddle of each assembly having an edge portiondisposed at an angle within the range 2337 to the radially extendingportion, and a second paddle of each assembly having an edge portiondisposed at an angle within the range 53-67 to the radially extendingportion whereby the variously angled paddles of the plurality of paddleassemblies cooperate to produce the equivalent effect of a substantiallyperpendicular direction of the etchant against the plate surface at anyspeed within the operating speed range.

6. The improvement as claimed in claim 5 wherein said first paddle ofeach assembly has an edge portion disposed at a 30 angle to the radiallyextending portion, and said second paddle has an edge portion disposedat a 60 angle to the radially extending portion.

7. The improvement as claimed in claim 6 wherein said first and saidsecond paddles are in substantially diametrically opposed relation onthe paddle assembly.

l t t I I 2 3 UNITED STATES PATENT OFFICE CERTIFICATE @F ECHQN PatentNo. 3,627,614 Dated December 14, 1971 Inventor(s) Louis E. Zeller andRobert J. Petsko It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 4, line 66, after "paddles" insert "for producing the equivalenteffect of-a substantially perpendicular direction of the etchant againstthe plate surfaces upon rotation of the paddle assemblies at any speedwithin the o erating speed range, said letter means comprising asubstantially greater angle of one peddle edge portion with respect toits radial portion then of the other paddle edge portion..

Signed and sealed this 30th day of May 1972.

- (SEAL) Attest:

EDWARD MoFLETGHER, JR. ROBERT GOTISCHALK Attesting Officer Commissionerof Patents

2. The improvement as claimed in claim 1 wherein each said paddleassembly includes a first paddle having an outer edge portion disposedat an angle substantially within the range 23* -37*, and a second paddlehaving an outer edge portion disposed at an angle substantially withinthe range 53* - 67*.
 3. The improvement as claimed in claim 1 whereinsaid paddle assembly includes a first paddle having an edge portiondisposed at a 30* angle, and a second paddle having an outer edgeportion disposed at a 60* angle.
 4. The improvement as claimed in claim3 wherein said first and second paddles are in diametrically opposedrelation on the paddle assembly.
 5. In an etching machine having a tankadapted to contain an etching bath, means for maintaining the bath at apredetermined level, means for supporting a photoengraving plate abovethe etching bath in spaced parallel relation with the surface of thebath, means for providing planar movement of said photoengraving plate,a plurality of paddle assemblies having spaced parallel horizontal axesrotatably disposed between the plate and the etching bath and adapted todirect etchant from the etching bath against the photoengraving platE,and selectively variable means for rotating said paddle assemblieswithin a range of operating speeds, the improvement wherein each saidpaddle assembly comprises a plurality of paddles, each paddle includingan inner radially extending portion and outer edge portion, the outeredge portions of the paddles of each assembly being variously angledwith respect to the radially extending portions in the direction ofrotation of the assembly, a first paddle of each assembly having an edgeportion disposed at an angle within the range 23* - 37* to the radiallyextending portion, and a second paddle of each assembly having an edgeportion disposed at an angle within the range 53* - 67* to the radiallyextending portion whereby the variously angled paddles of the pluralityof paddle assemblies cooperate to produce the equivalent effect of asubstantially perpendicular direction of the etchant against the platesurface at any speed within the operating speed range.
 6. Theimprovement as claimed in claim 5 wherein said first paddle of eachassembly has an edge portion disposed at a 30* angle to the radiallyextending portion, and said second paddle has an edge portion disposedat a 60* angle to the radially extending portion.
 7. The improvement asclaimed in claim 6 wherein said first and said second paddles are insubstantially diametrically opposed relation on the paddle assembly.